This invention relates to anemometers, and more particularly to an anemometer having an improved bearing arrangement for supporting thrust and axial loads imposed on an anemometer rotor.
Anemometers include a rotor with radially extending blades for catching wind or other fluid flow which causes the rotor to spin about its axis. Wind speed or fluid flow rate is directly proportional to the revolutions of the rotor in a given period of time, and a transducer coupled to the rotor converts the rotational speed of the rotor into a corresponding electrical output signal proportional to wind speed or fluid flow rate.
The present invention provides an anemometer which provides accurate readings over an extended period of use in potentially destructive or corrosive environments such as in refineries, heating systems of buildings, steam power plants, and the like. In such environments where a sensitive instrument, such as an anemometer, can be subjected to hot air or steam, including superheated steam in the order of 700.degree. F., corrosion of working surfaces of the instrument can lead to premature failure. Bushings of metal and stellite with tungsten carbide wear badly due to removal of the protective oxide coating, due to rubbing. Ball bearings with no lubricant also have intimate contact and wear due to rubbing.
This invention provides an improvement over a prior art anemometer which resulted in premature bearing failure when operated in a live steam environment at approximately 700.degree. F. This condition precludes the use of bearings requiring lubrication, and therefore solid bearing surfaces were used in the prior art anemometer. The rotor blade assembly in the prior art anemometer was rigidly secured to a rotatable axial shaft. The rotor shaft was made of tungsten carbide, and the opposite ends of the shaft rotated in stellite front and rear bushings. During use of the prior art anemometer, severe wear occurred at the upstream or front bushing, which caused increased orbiting of the rotor shaft within its working clearance in the upstream bushing. Such orbiting increased to a point where the pickup coil sensed the wobble of the rotor shaft and produced erratic readings. The useful life of the anemometer was between three to five hours.
Thus, there is a need for an anemometer which can provide accurate readings when used in potentially destructive or corrosive environments, such as a superheated live steam environment, over an extended period of time.